Keying control system



Jan. 25, 1949.

s. CHAPIN KEYING CONTROL SYSTEM Filed July 8, 1946 ,INVENTOR; Y Riv/V040 5. CHAP/A/ BY 5% ATTO/P/Vf Patented Jan. 25,1949

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. Reynolds;ohapm mushing. N: Y;, assignor to Bress.-Wireless;- Inca -iNew Yor-k -sN; Y.,...acorporation. oftDel-awarea App-neauonmys; 1946, Serial No: 6812820 1-;Claim.

This invention: relates ito" telegraph signalling systems and more particularly? to channel keying control arrangements 1 therefor;

A principal object ofthe inventionis' to' provide improved electron tube and associated cir'-- cuit arrangements for-keying 'on-and ofi""two telegraph-signalling channels.

Another object is to provide-improved electrontube and associated circuit arrangements for keying on and oil tone'irequencies under-"con trol of impressed telegraph signals-of the neutral type-orof the-'polar'type' A feature ofthe'invention relates" to" a novel combination of-grid-controlled electrontubes-for selectively connecting -eitl'ier one of two"-tone-frequenciesto a commonoutput channel; undercon trol of input telegraph signals either of the polar type or of the-neutral type:

Another feature relates. to..a. keying control arrangement for-telegraphsignalling systems and the like whereby. a pair of input signals such for example as the tone frequeneies,can--be alternately switched to a common output circuit under controlof polar or neutral telegraph signals, and requiring no balancing. adjustment while preserving the output signaL-fre wfrom switching transients. v

A still further featurerelates to the novel"'organization, arrangement and relative interc'on' nectionof. parts which cooperatez to provid'e an improved tone keyer arrangement.

Other features and advantages not specifically enumerated will become apparent after a consideration of the following detailed descriptions and the appended claim.

In the drawing.

Fig. 1 is a schematic wiring diagram of a typical telegraph keying system embodying the invention. 7

Fig. 2 is a graph showing the types of signals to be keyed in the system of Fig. 1.

In the drawing, the terminals A and B represent input terminals on which are impressed respectively two difierent input signals. For example, these signals may be in the form of tone frequency voltages of difierent frequencies as represented by the signals A and B (Fig. 2). Thus ths signal A may have a frequency of 2400 C. P. S., and the signal B, a frequency of 1200 C. P. S.

The terminals C represent a common output channel which may be connected to a signal receiving or rekeying device It] of any well-known type which is adapted to respond selectively to (Cl. 250-27 )J 2 telegraph signals l ll' which: produces either: theneutral t ype of 'sig-nal as representedbygraph l2:

wherethesignalivoltage varies on one side'oif'zero. voltage; orapolarsignal 1 l 3'Zwhichva'riest equally onopposite" positive and negative sides of" zero.

It' will 'be understood that the keying. frequency of 'the signals applied to'terminals D is lower than either of: the" frequencies 1A and-B.

The signal A .is applied through couplingcon-- denser IS betWeenthe cathode if; of grid-control tube It and ground; Whereas the signalf B "is ap'-- plied between a the control grid ll of dual triode tube' IS and-ground; by meansof conden'serw A- suitable high resistance grid leakis provided inthe usual manner between'the grid il-and ground.

Consequently, the B signals-applied to grid-ll are amplified in the first triodesection of tube IB and"app'ear-ascorresponding output voltages aeross the plateload resistor 21 The second triode sectionof tube- I 8 has its control grid 22 connected in parallel'with the control grid-'23 of tube-16 The cathodes 24 -and 25 are returned to ground through a common cathode load resister-"2'51- Theplate-or anode" 2 3 is connected-di rectlyto: thef-plusxBx-terminal ofthe usual DaC.

latepower "suqoply. (not shown) With tliis=connection -of the" triode sections of tube-i8} this tube forms: a limiter of" thetype' disclosedl' intU." S; Patent #2276555 toiwhich referen'ce may. be had for: a: further description. of the operation-thereof as a limiter; When" no. signals are applied from source I I to the grid 23, the tube I6 is biased substantially to plate current cutofi by means of the fixed bias battery 23 and resistor 29. Under these conditions however, the triode section ll, 25, 39, is plate current conductive and permits the B signal applied at terminals B to be amplified and appear as corresponding amplified voltages across load resistor 21. In other words, as long as tube it is at outofi, the signals at terminals B appear across the load resistor 2i; Since the grid 23 is normally biased negatively with respect to its cathode to plate current cutoif, it is apparent that if a signal of the polar type and having a negative voltage value is applied to grid 23, this last-mentioned condition is not disturbed, with the result that the B signals continue to appear across the resistor 2 I. On the other hand, if a positive polar signal is applied to grid 23 or if an on positive neutral signal is applied to grid 23, the negative bias of tube 5 is overcome permitting plate current to flow through tube l5, resulting in the appearance of amplified A signals across resistor 2 I. At the same time, this positive input voltage is applied to control grid 22, causing a large plate current to flow between anode 21 and cathode 24 and thence through the common cathode load resistor 26. across resistor 26, the grid I1 is biased negatively to a sufiicient extent to cutoff plate current flow between 3i? and 25, thus positively cutting off the cathode causing tube 15 to be plate conductive and the A signals appear across resistor 2|.

Thus, for a change in Voltage at grid 23 from negative to positive polarity or from zero to pos1- I tive polarity, the signal appearing across resistor 2i haschanged from the signal B to thesignal A. Furthermore, at an intermediate point of the positive signal appliedto grid 23, neither signal A nor signal B, appears across resistor 2|.

In addition to the A and B signals which alternately appear across resistor 2!, there is present the frequency of the signal applied to grid 23. For this purpose, the output terminals C are coupled to resistorVZI through a high pass filter which is designed to have its cutoff frequency located between the frequency of themput signals to grid '23 and the frequency of signal B which is the lower of the two signals A and B. As a result, only these signals A andB appear at the common output terminal C.

While in this specification and the appended claims, reference is made to the tubes as triodes, it will be understood that the term triode is used in its generic sense to include any gridcontrolled tube havinga control grid which can be suitably biased to control the on and off flow of plate current as is well-known in the art. Furthermore, While in the foregoing specification the sources A and B have been, referred to as audio frequency tone sources, it will be understood that the invention is equally well usable with sources A and B of any other frequency range such as radio frequencies in which event of course the high pass filter will be designed to pass the radio frequencies from the sources A and B while suppressing or eliminating the key- As the positive voltage of the signal applied to grids 22 and 23 increases in amplitude, it finally overcomes the bias on the 1 As a result of this drop of voltage 4 ing control frequencies from the source H. The terminals 0 can then be connected to any suitable radio frequency power amplifier, thus enabling the system to be used for so-called carrier frequency shift transmission.

While one particular embodiment has been described, it will be understood that various changes and. modifications may be'mad'e herein Without departing from thespirit and scope of the invention.

What is claimed is:

An arrangement of the character described,

comprising a first trlode, a first source of input Signals coupled to the cathode of said first triode, a

secondtriode, a second source of input signals connected to the control grid of said second trlode,

a third triode having its control grid connected in parallel withthe 'control grid of the first triode, a common load resistor connected between the cathodes, of the second and third triodes and ground, means normally biasing the cathode of the firsttriode to plate current cutoff, while the second triode is plate conductive, means to apply a control signal of a certain magnitude to the control grids of-the said first and third triodes without disturbing the plate, current cutoff of the first triode and the plate current conductivity of the second triode, and for applying a control signal of a different magnitude to the control grids of the first and third triodes to render the first triode plate conductive while simultaneously rendering the second triode non plate conductive through the intermediary of the voltages developed across said common cathode resistor, and a common plate load circuit connected to the plates of the first and second triodes.

v REYNOLDS. CHAPIN. REFERENCES orrnn 'The following references are of record in the file of this patent:

UNITED STATES PATENTS 

